The invention relates to undesired interference at connection points in conductors, i.e. to disturbance and interference in low-voltage connectors.
When discussing undesired interference, the term electro-magnetic compatibility (EMC) is usually used. All undesired interaction between a device, conductors or the surroundings thereof is considered interference. In connectors, the connection may be of conclusive importance with respect to the EMC properties of a device, so the significance of the connectors used in the connections of conductors should not be underestimated.
In low-voltage (LV) systems, in which the voltage does not exceed 1,000 V ac or 1,500 V dc, power supply lines and the control wires of actuators are typically places, where interference is conventionally eliminated from electric connectors by directing the interference from the connection to the ground of the body.
Shielding in connectors is conventionally implemented by installing a shielding means, such as a capacitor, between the connection and the ground of the body. Such an arrangement results in external connections, and the connections are exposed to contact and may break and cause a poor contact. Poor connections or incorrectly shielded connectors cause extra interference radiation.
Another problem in the above arrangement is the fastening of the capacitor or other shielding means, The shielding means requires space and is difficult to fasten. To facilitate installation, the conductors must be sufficiently long to make manual installation possible. A weakness in such an installation arrangement is a poor interference-class quality level caused by the long conductors of the shielding arrangement and an installation susceptible to interference. Due to the difficult fastening, the interference-class quality level often depends on the installer of the shielding arrangement and is, thus, difficult to predict.
It is thus an object of the invention to develop a shielding arrangement and a connector implementing the arrangement in such a manner that the above-mentioned drawbacks can be avoided. The object of the invention is achieved by a shielding arrangement and connector that are characterized by what is stated in the independent claims. Preferred embodiments of the invention are described in the dependent claims.
The invention is based on the idea that a shielding arrangement and connector are arranged to a connector in such a manner that the shielding arrangement can be implemented in a secure manner inside the connector. The connector of the invention is arranged such that the shielding means can be placed inside the connector.
The conductors of the shielding arrangement of the invention can be made very short without affecting the installability. In many cases, it is possible to implement the shielding arrangement in the connector of the invention without separate conductors by utilizing the pins of the shielding means, such as the pins of the capacitor.
The shielding arrangement and connector of the invention provide a very short electric distance from the connector to the body serving as the grounding point, whereby interference is reduced. Too high impedance is then not generated by the conductors and connections of the shielding arrangement.
The size of the conductors entering the connector is often not known in advance, so the part of the connector receiving the conductor often needs to be oversized. The receiving part of the connector is often adjustable so as to fasten conductors with different conductor surface areas. The conductor surface area of the adjustable receiving part may vary between 25 and 95 mm2 or 95 and 185 mm2, for instance.
It is often possible to define the size of the outgoing conductor in advance. The outgoing conductor is almost invariably smaller than the largest possible conductor surface area of the receiving part. The outgoing conductor then does not require as much space from the connector. The space requirement of the outgoing conductor-side connection is thus smaller than that of the receiving part. The connector of the invention utilizes this space requirement difference by arranging on the side of the outgoing conductor a hollow space enabled by the space requirement difference. The shielding means can be placed in this hollow space in such a manner that the body part covers the shielding means placed in the space.
In the arrangement of the invention, the length of the shielding conductors is made as short as possible without affecting installability. The grounding of the shielding means installed between the connector and base can according to the invention be implemented by a connecting means and grounding strip, in many cases completely without separate conductors. The connection can then be made directly to the shielding component, such as to the pins of the capacitor, thus eliminating the two connection points that were earlier needed with the use of conductors and are vulnerable with respect to interference and reliability. The elimination of these two connection points is a particular advantage for shielding in a connector, and is obtained by arranging the shielding means inside the connector.
By using the grounding strip, the grounding point can be brought close enough to connect the pin of the shielding means directly to the grounding strip. Moving the grounding point close to the shielding means is done with the grounding strip that is arranged to shift interference as well as possible onward from the means to the base. The grounding strip is made of an electrically conducting material and its surface area is as large as possible. The size of the grounding strip is arranged such that, when the grounding strip is on the bottom surface of the connector body and the body is attached to the base, the grounding strip is covered under the body. The grounding strip is fastened to the base with the body by means of an electrically conducting fastening means, such as a screw.